This invention relates to systems circulating and cooling a liquid coolant, or the like, and particularly to apparatus for indicating the quantity of liquid in the system, which apparatus is temperature compensated to obviate false indications due to temperature change. A circulating system of the kind set forth includes an accumulator-reservoir device maintaining pressure in the system and accommodating temperature induced expansion of the coolant.
It is desirable for obvious reasons to indicate the quantity of liquid in a liquid coolant circulating system. Such inidication is complicated, however, by the fact that the density of the coolant increases and reduces in an inverse relation to temperature change. It is not possible, therefore, to make an accurate reading of coolant quantity unless temperature effects are compensated for. The prior art contains examples of temperature compensated indicators. However, in known instances these examples are directly associated with accumulator-reservoir devices in the system, or, in an electrical version, resistance variations in a potentiometer are analyzed by an electronic circuit. The former examples require access to and direct reading of a scale on the accumulator-reservoir device. The latter have a "black box" mysticism involving specialized manufacture and servicing. Also, in some instances, as in aircraft use, generated electrical noise and magnetic effects may be regarded as objectionable.